SOS G R A 
Thofe who have nature’s fteps with care purfii’d, 
That matter is with aftive force endy’d, 
That all its parts magnetic pow’r exert, 
And to each otlier gravitatt, affert. Blackmore. 
GRAVITA'TION, /. A6t of tending to the centre, 
—The mofi; confiderable phenomenon belonging to the 
terrertrial bodies is the general a6tion of gravitation, 
whereby all known bodies, in the vicinity of the earth, 
do tend and prefs towards its centre. Bentley. 
V/hen the loofe mountain trembles from on high, 
Sliall gravitation ceafe, if you go by f Pope. 
It is one of the laws of nature, difcovered by New¬ 
ton, and now received by all philofophers, that every 
particle of matter in nature gravitates towards every 
other particle ; which law is the main principle in the 
Newtonian philofophy. But what is called gravitation 
with refpedt to the gravitating body, is ufiially called 
attraBion with refpetl to tire body gravitated to. The 
planets, both primary and fccondary, as alfo the comets, 
do all gravitate towards the fun, and towards each 
other} as well as the fun towards them; and that in 
proportion to the quantity of matter in each of them. 
The peripatetics indeed hold, tliat bodies only gravi¬ 
tate or weigh, when out of their natural places, and that 
gravitation ceales when they are reflored to tire fame, 
the purpofe of nature being then fulfilled ; and they 
maintain that the final caufe of this faculty is only to 
bring elementary bodies to their proper place, where 
they may reft. But the moderns iliew that bodies ex- 
ercife gravity even when at reft, and in their proper 
places. ‘ This is particularly fiiewn of fluids; and it is 
one of the laws of hydrolfatics, tliat fluids gravitate in 
proprio loco, the upper parts preffing on the lower, &c. 
See the article Mechanics. 
GPvAV'ITY,^. \_graviias, Lat. gravite, Fr. ] Weight ; 
heavinefs ; tendency to the centre.—Bodies uo fwim or 
fink in ditferent liquors, according to the tenacity or 
gravity of thofe liquors which are to fupport them. 
Brown. —Atrocioufnefs ; weight of guilt.—No man could 
ever have thought this realonable, that had intended 
thereby only to punilh the injury committed, according 
to the gravity of the faCf. Hooker. —Serioufnels ; folcm- 
nity.—For tiie advocates and council iliat plead, pa¬ 
tience and gravity of liearing is an eli'entiai part of juf- 
tice. Bacon. 
In phyiics, the terms gravity, weight, centripetal force, 
and attraBion, denote in ettedt much the lame thing, 
o.niy in dilterent views and relations ; all which how¬ 
ever it is too coinnion to confound and ule promifeu- 
oully. But,,,'Coirectly, w-hen a body is confidered as in 
the art of tending towards the earth, the force with 
whicli it lo rends is called force of gravity, or gravitating 
force: for wliich fed Mechanics. Wneiithe body is 
confidered as immediately tending to the centre ot the 
earth, it is called centripetal force : fee the article 
Fluxions, vol. vi. p. 516. When we confider the 
earth, or im.fs, or matter, to which tlie body tends, it 
is Called attraBion, or attraBive force: lee CH.iMiSTRV, 
voi. iv. p. 174. When it is co.ilidered in reipcit of an 
obftacle or another body in the way of the tendency 
upon which it .lits, it is called weight: lee Mechanics. 
Philolophers have argued very difiercntly onthefub- 
je^t of gr.ivity. Newton, though he often c. lls it a 
vis, power, or property in bodies, yet explains hinil'elf, 
tiuit lie means nothing more by the woid but the eliect 
or phenomenon : he does not conlider the principle tlie 
caule by which bodie.s tend downwards, but the tendency 
itfelf, w iiicli is no occult quality, but a lenlible plteno- 
iiieiion, be as cauies wi'.atevci they may ; tlie laws or 
propel ties relating to v. iiich are as follow : 
All bodies which circunilcribe, furround, or exift 
upion or above, the eaitii, tend towards a point, which 
is eitlutr accurately or very nearly tiie Centre ot magni¬ 
tude of the te-iraqucous globe.- irience, iir all places 
G R A 
equidiftant from the centre of the earth, as fuppofe m 
the degrees or minutes of a circle furrouiiding the 
whole, if perpendiculars or weights were let fall, tliey 
would all meet and coalefce in the centre of the earth. 
It mull however be recollerted, that all the parts of 
the earth’s furface are not at equal dillances from the 
centre, becaufe the equatorial parts are higher than the 
polar parts by about feventeen miles ; as has been fhewn 
under the arricle Astronomy. 
Gravity equally afferts all bodie*, without regard ei¬ 
ther to tlieir bulk, figure, or matter : fo tha*-, abftrart- 
ina from the refiftance of the medium, the moft com¬ 
part and loofe, the greateft and finalleft, bodies, would 
all defeend through an equal fpace in the lame time; 
whence the force of gravity is nearly equal, as appears 
from the quick defeent of very light bodies in an ex- 
haufted receiver. The fpace which bodies do artualfy 
fall, in vacuo, is 16^ feet in tlie fiift fecond of time, in 
the latitude of London; and for other times, cither 
greater or lefs than that, the fpaces defceiided from 
are diredfly proportional to tiie fquares of the times, 
while the falling body is not far from the earth’s fiir- 
face. This power is the greateft at the earth’s furface, 
from whence it decreafes both upwards and downwards, 
but not both ways in the fame proportion ; for upwards 
the force of gravity is lefs, or decreafes, as the fquare 
of the diftance from the centre increafes ; fo that at a 
double diftance from the centre, above the furface, the 
torce would be only one.fourth of what it is at the fur¬ 
face ; but below the liirface, the power decreafes in 
fuch fort that its intenfity is in the direct ratio of the 
diftance from the centre ; fo that at the diftance of half 
a temidiameter from the centre, the'force would be but 
half what it is at the furface ; at one-third of a feiiii- 
diameter the force would be one-third, and fo on. 
As aii bodies gravitate towards the earth, i'o does the 
earth equally gravitate towards all bodies ; as well as 
all bodies towards particular parts of the eartli, as hills, 
&c. which has been proved by the attraction a hill has 
upon a plumb line, inlenlibly drawing it afide. Hence 
tlie gravitating force of entire bodies conftfts of thole 
ot all tlieir parts; for by adding or taking away any 
part of tlie matter of a body, its gravity is increafed or 
decreafed in the proportion of the quantity of fuch por¬ 
tion to the whole mals. Fience alio the gravitating 
powers of bodies, at tlie fame diftance from the centre, 
are proportional to the quantities of matter in the bodies. 
But for the dottrine of the Centre of Gravity, and Cerltral 
Forces, fee tiie articles Fluxions, and Mechanics. 
1 lie exiftence of the fame principle of gravity in the 
fuperior regions of the heavens, as on the earth, is one 
of the great dlfcoveries of Newton. At fiift he only 
obferved that all bodies near the eartJi, and in its at- 
mofplieie, had tlie property of tending diredtly towards 
it ; but at lengcli he law uo realoii wliy it might not ex¬ 
tend as far as to the moon, by means of which ihe might 
be retained in her orbit as a ftoiie in a fling is retained 
by tlie hand ; and if lo, he next inferred, wliy might 
HOC a limilar principle exift in the otiier great bodies in 
the univeife, ihe lun and all the other planets, both 
primary and fecondary, which might all be retained in 
their orbits, and perform their revolutions, by ineaas of 
the fame univerlal principle of gravity. I hefe conjec¬ 
tures tie loon lealiEed and verified by niaihcmat.cal 
proofs. Kepler iiad lound out, by contemplating tlie 
motions of tiie planets about tiie fun, tliat the ..lea de- 
feribed by a line connerting ihc lun and planer, as this 
revolved in its orbit, uas always proportional to the 
lime oi iis delcription, or liuti it deferibed .‘-qua! areas 
in equal iin.es, in wii. itvti part of its orbit liie planet 
iiiigiit be, moving always lo much tne quiti cr us its 
diliance trom tlie lun was iels. And it is ai.o lound 
tint the latellitcs, 01 lecondary j h.nns, refpect the lame 
iavv ill revolving aucni ineir priiii„iies. Ji was next 
proved by Newton, that all bodies moving in any curve 
line 
